Field of the Invention
The present invention relates to a multilayer ceramic capacitor constituted by a capacitor body of roughly rectangular solid shape, which has a first external electrode and a second external electrode provided with a space between them on one of the two height-direction surfaces of the capacitor body in the length direction.
Description of the Related Art
Multilayer ceramic capacitors 100 like the one shown in FIGS. 1A and 1B are known as a way to make a multilayer ceramic capacitor smaller while increasing its capacitance at the same time (e.g., those disclosed in Japanese Patent Laid-open No. 2014-160693, the disclosure of which is incorporated herein by reference to the extent consistent with the instant disclosure). FIG. 1A is a drawing that shows a multilayer ceramic capacitor 100 as viewed from one of its two width-direction surfaces, while FIG. 1B is a drawing that shows the multilayer ceramic capacitor 100 in FIG. 1A as viewed from one of its two height-direction surfaces. It should be noted that, for the purpose of convenience, FIG. 1B is drawn in such a way that the exposed parts (refer to the bold lines) of the lead parts 104a, 105a described later are visible from the outside of the first external electrode 102 and second external electrode 103, respectively.
The multilayer ceramic capacitor 100 shown in FIGS. 1A and 1B is constituted by a capacitor body 101 of roughly rectangular solid shape, which has a first external electrode 102 and a second external electrode 103 provided with a space between them on one of the two height-direction surfaces of the capacitor body 101 in the length direction. Also, the capacitor body 101 has a built-in capacitive part comprising multiple first internal electrode layers 104 and multiple second internal electrode layers 105 stacked alternately in the width direction with dielectric layers in between. Furthermore, a lead part 104a of each first internal electrode layer 104 is exposed on one of the two height-direction surfaces of the capacitor body 101, with this exposed part connected independently and electrically to the first external electrode 102, while a lead part 105a of each second internal electrode layer 105 is exposed on one of the two height-direction surfaces of the capacitor body 101, with this exposed part connected independently and electrically to the second external electrode 103.
Because its first external electrode 102 and second external electrode 103 are provided on one of the two height-direction surfaces of the capacitor body 101, this multilayer ceramic capacitor 100 can prevent, to the maximum extent possible, the external dimensions of the capacitor body 101 from being limited by the first external electrode 102 and second external electrode 103, compared to when the external electrodes have an L-shape, horizontal U-shape, quadrangular cylinder shape with bottom, or the like.
This means that, even when the external dimensions of the multilayer ceramic capacitor 100 are small, the capacitor body 101 can be designed with the maximum possible external dimensions, which in turn allows the contour dimensions of the first internal electrode layer 104 and second internal electrode layer 105 to increase, respectively, thereby increasing the area of the internal electrode layers facing each other, and achieving a larger capacitance as a result.
With the multilayer ceramic capacitor 100 shown in FIGS. 1A and 1B, ideally the positions on one of the two height-direction surfaces of the capacitor body 101 where the first external electrode 102 and second external electrode 103 are formed, as well as their contour shapes, correspond to the forming positions and contour shapes shown in FIG. 1B.
However, the present inventors realized the following problems. That is, it is technically difficult to form both the first external electrode 102 and second external electrode 103 on one of the two height-direction surfaces of the capacitor body 101, and particularly when the external dimensions of the capacitor body 101 become smaller, the frequency at which the forming positions and contour shapes of the first external electrode 102 and second external electrode 103 differ from the ideal forming positions and contour shapes, respectively, becomes higher.
FIGS. 2A through 3D each provide drawings that explain conditions where the forming positions and contour shapes of the first external electrode 102 and second external electrode 103 differ from the ideal forming positions and contour shapes, respectively (refer to FIG. 1B). It should be noted that, while FIGS. 2A through 3D each illustrate the first external electrode 102 alone for the purpose of convenience, the modes in which the forming position and contour shape of the second external electrode 103 differ are the same as those shown in each of FIGS. 2A through 3D. Also, FIGS. 2A through 3D are each drawn in such a way that the exposed part (refer to the bold line) of each lead part 104a is visible from the outside of the first external electrode 102. Furthermore, while the contour shape of the first external electrode 102 in FIGS. 2A through 2D, and those in FIGS. 3A through 3D match the contour shape of the first external electrode 102 shown in FIG. 1B for the purpose of convenience, it goes without saying that each contour shape may differ from the contour shape of the first external electrode 102 shown in FIG. 1B.
FIG. 2A shows a condition AP1 where the first external electrode 102 is displaced significantly outward in the length direction and the exposed parts of all lead parts 104a are partially revealed, FIG. 2B shows a condition AP2 where the first external electrode 102 is displaced significantly inward in the length direction and the exposed parts of all lead parts 104a are partially revealed, FIG. 2C shows a condition AP3 where the first external electrode 102 is displaced significantly outward in the width direction and one of the exposed parts of all lead parts 104a is revealed, and FIG. 2D shows a condition AP4 where the first external electrode 102 is displaced significantly inward in the length direction and outward in the width direction and one of the exposed parts of all lead parts 104a is revealed and the other exposed parts are partially revealed, as well as a condition AP5 where the first external electrode 102 is displaced significantly outward in the length direction and also outward in the width direction and one of the exposed parts of all lead parts 104a is revealed and the other exposed parts are partially revealed (refer to the two-dot chain line).
Also, FIG. 3A shows a condition AP6 where the first external electrode 102 is displaced slightly outward in the length direction but the exposed parts of all lead parts 104a are covered by the first external electrode 102, FIG. 3B shows a condition AP7 where the first external electrode 102 is displaced slightly inward in the length direction but the exposed parts of all lead parts 104a are covered by the first external electrode 102, FIG. 3C shows a condition AP8 where the first external electrode 102 is displaced slightly outward in the width direction but the exposed parts of all lead parts 104a are covered by the first external electrode 102, and FIG. 3D shows a condition AP9 where the first external electrode 102 is displaced slightly inward in the length direction and outward in the width direction but the exposed parts of all lead parts 104a are covered by the first external electrode 102, as well as a condition AP10 where the first external electrode 102 is displaced slightly outward in the length direction and also outward in the width direction but the exposed parts of all lead parts 104a are covered by the first external electrode 102 (refer to the two-dot chain line).
Incidentally, an appearance inspection of the forming positions and contour shapes of the first external electrode 102 and second external electrode 103 formed on one of the two height-direction surfaces of the capacitor body 101, respectively, has been performed using an image-processing apparatus. In the appearance inspection, those samples with the exposed parts of all lead parts 104a, 105a not covered by the first external electrode 102 and second external electrode 103, respectively, are found defective, while those samples whose first external electrode 102 and second external electrode 103 are projecting outward from at least one of the judgment criterion length and width, respectively, are found defective. It should be noted that, with the capacitor body 101 shown in FIGS. 1A and 1B, the two height-direction surfaces have the same length and width and therefore the criterion length and criterion width described below are different from the length and width of one of the two height-direction surfaces, or from the length and width of the other of the two height-direction surfaces.
In other words, the five conditions AP1 through AP5 explained using FIGS. 2A through 2D are found defective because the exposed parts of all lead parts 104a, 105a are not covered by the first external electrode 102 and second external electrode 103, respectively. Of the five conditions AP6 through AP10 explained using FIGS. 3A through 3D, on the other hand, the condition AP7 is found non-defective because neither the first external electrode 102 nor second external electrode 103 is projecting outward from either the criterion length or criterion width. The remaining four conditions AP6 and AP8 through AP10 are found defective because the first external electrode 102 and second external electrode 103 project outward from at least one of the criterion length and criterion width, respectively.
Among the five conditions AP6 through AP10 explained using FIGS. 3A through 3D, however, the four conditions AP6 and AP8 through AP10, excluding the condition AP7, are extremely unlikely to present problems in function or in use because, although the first external electrode 102 and second external electrode 103 are projecting slightly outward from at least one of the criterion length and criterion width, respectively, the exposed parts of all lead parts 104a, 105a are covered by the first external electrode 102 and second external electrode 103, respectively.
In other words, applying to a multilayer ceramic capacitor such ingenious ideas that allow several of the four conditions AP6 and AP8 through AP10 that are extremely unlikely to present problems in function and in use, to be found non-defective in the appearance inspection, should improve yield and help reduce cost.
Any discussion of problems and solutions involved in the related art (particularly those discussed above) has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.